This disclosure relates to nanocomposite microgel compositions comprising a polymer and a water-swellable mineral nanoclay, their methods of manufacture, and their uses. The disclosure also relates to water swellable compositions comprising the nanocomposite microgels and articles containing the water swellable compositions.
Hydrogels are hydrophilic polymer networks that can absorb large amounts of water from aqueous solutions without being dissolved. These networks can be synthesized through chemical or physical cross-linking.
Nanocomposite microgels have a three-dimensional network structure and a water-swellable mineral nanoclay crosslinking the network structure. Nanocomposite microgels can possess enhanced swelling properties based on their unique polymer/nanoclay network structure, for example the ability to dramatically swell or shrink in response to a variety of external stimuli such as temperature, pH, ionic strength, electric field, and enzyme activities. These properties make them useful in a wide variety of applications, for example, swellable rubber compounds for the oil and gas industry, superabsorbents for hygienic and agricultural applications.
The nanocomposite hydrogel is typically manufactured by the polymerization of water-soluble monomers in an aqueous medium in the presence of a water-swellable nanoclay, and an aqueous polymerization initiator. Thus formed hydrogel is then isolated, and can be dried to form a nanocomposite microgel. One drawback to the nanocomposites is that they are obtained as relatively large particles, for example on the order of 100 to 300 micrometers. Another drawback to thus formed nanocomposite hydrogels is that they are synthesized in bulk form, the specifics of which are determined by the shape of the mold, for example thin film, sheets, rods, hollow tube, cubes, spheres, and bellows. Even if size reduction of the nanocomposite microgels can be achieved by high-energy physical means, such as ball milling, hammer milling, or knife milling, typically results in large particle sizes and a broad particle size distribution, which requires further subsequent classification and waste of the particles not within the desired range.
There accordingly remains a need in the art for nanocomposite microgels having improved particles size distribution in the lower ranges and exhibiting better elastomeric behavior, greater swelling ratio and faster swelling kinetics compared to conventional super absorbent polymer (SAP) gels. There also remains a need for more efficient methods for the production of such nanocomposite micro gels.